Institute of Transportation, MOTC

　　In the project, the relationship between visual adaptation and illumination levels in long tunnels was investigated through two experiment stages. The first experiment stage was conducted in a simulated long tunnel laboratory. By controlling the time in the threshold zone, the subjects’ visual acuity, visual fatigue, and reaction time were measured; sixty subjects participated in this experiment. The second stage was a field study. From the results of the experiments, one can calculate the safe stopping distance and the appropriate threshold zone length. The results indicated that the drivers of this country need longer adaptation time than international regulations (i.e. 4 second). Some suggestions were proposed to revise the regulation rules for criteria.